goinstall: add -clean flag

R=adg, rsc
CC=golang-dev
https://golang.org/cl/3821042

src/cmd/goinstall/main.go

@@ -41,6 +41,7 @@ var (
 	reportToDashboard = flag.Bool("dashboard", true, "report public packages at "+dashboardURL)
 	logPkgs           = flag.Bool("log", true, "log installed packages to $GOROOT/goinstall.log for use by -a")
 	update            = flag.Bool("u", false, "update already-downloaded packages")
+	clean             = flag.Bool("clean", false, "clean the package directory before installing")
 	verbose           = flag.Bool("v", false, "verbose")
 )
 

src/cmd/goinstall/make.go

@@ -17,18 +17,27 @@ import (
 // For non-local packages or packages without Makefiles,
 // domake generates a standard Makefile and passes it
 // to make on standard input.
-func domake(dir, pkg string, local bool) os.Error {
+func domake(dir, pkg string, local bool) (err os.Error) {
+	needMakefile := true
 	if local {
 		_, err := os.Stat(dir + "/Makefile")
 		if err == nil {
-			return run(dir, nil, "gomake", "install")
+			needMakefile = false
 		}
 	}
-	makefile, err := makeMakefile(dir, pkg)
-	if err != nil {
+	cmd := []string{"gomake"}
+	var makefile []byte
+	if needMakefile {
+		if makefile, err = makeMakefile(dir, pkg); err != nil {
 			return err
 		}
-	return run(dir, makefile, "gomake", "-f-", "install")
+		cmd = append(cmd, "-f-")
+	}
+	if *clean {
+		cmd = append(cmd, "clean")
+	}
+	cmd = append(cmd, "install")
+	return run(dir, makefile, cmd...)
 }
 
 // makeMakefile computes the standard Makefile for the directory dir